Snowmobile fuel tank

ABSTRACT

A fuel tank includes a lower fuel tank wall and an upper fuel tank wall. The lower fuel tank wall is connected to an inner surface of the upper fuel tank wall. Each of the lower and upper fuel tank walls is constructed of a single piece of sheet metal. The lower and upper fuel tank walls enclose a volume therebetween configured to be in fluid communication with an engine of a vehicle.

CROSS-REFERENCE

The present application is a continuation of U.S. patent applicationSer. No. 15/505,264, filed on Feb. 21, 2017, which is a national phaseentry of PCT Patent Application No. PCT/IB2015/056604, filed on Aug. 31,2015, which claims priority to U.S. Provisional Patent Application No.62/043,966 filed on Aug. 29, 2014, the entirety of each of which isincorporated herein by reference.

TECHNICAL FIELD

The present technology relates to fuel tanks for snowmobiles.

BACKGROUND

Snowmobiles are designed for travel on groomed trails as well asoff-trail areas, and for different uses such as recreational purposes orfor carrying loads. It is therefore desirable to design snowmobileframes to be rugged so that they can withstand different kinds ofcompression and torsional forces experienced while driving on differentterrains and under different conditions.

For improved fuel efficiency and for better handling of a snowmobile indifferent riding conditions, it is also desirable to reduce the weightof the frame.

SUMMARY

One object of the present is to ameliorate at least some of theinconveniences of the prior art.

According to one aspect of the present technology, there is provided afuel tank including a lower fuel tank wall and an upper fuel tank wall.The lower fuel tank wall is connected to an inner surface of the upperfuel tank wall. Each of the lower and upper fuel tank walls isconstructed of a single piece of sheet metal. The lower and upper fueltank walls enclose a volume therebetween configured to be in fluidcommunication with an engine of a vehicle.

In some implementations, the vehicle is a snowmobile having a tunnel anda forward support. The fuel tank is configured to be removably connectedto the tunnel and the forward support of the snowmobile by the upperfuel tank wall. The upper fuel tank wall inclues: a left lower endportion for connecting the fuel tank to the tunnel on a left side of alongitudinal centerplane of the snowmobile; a right lower end portionfor connecting the fuel tank to the tunnel on a right side of alongitudinal centerplane of the snowmobile; and an upper end portion forconnecting the fuel tank to the forward support.

In some implementations, the upper fuel tank wall includes: a left sideportion extending generally vertically and including the left lower endportion; a right side portion extending generally vertically andincluding the right lower end portion; and a central portion beingformed integrally with the left and right side portions. The left sideportion extends generally upwardly from the left lower end portion tothe central portion. The right side portion extends generally upwardlyfrom the right lower end portion to the central portion. The centralportion extends laterally between the left and right side portions.

In some implementations, the lower fuel tank wall extends generallyhorizontally from the left side portion to the right side portion of theupper fuel tank wall.

In some implementations, the upper fuel tank wall defines a fill openingin fluid communication with the volume.

In some implementations, the fuel tank also includes at least one seatfastening member for fastening a seat of the vehicle to the fuel tank.The at least one seat fastening member is connected to an outer surfaceof the upper fuel tank wall facing away from the lower fuel tank wall.

In some implementations, each of the upper and lower fuel tank walls isformed by one of stamping and super plastic forming.

In some implementations, each of the left and right lower end portionsof the upper fuel tank wall defines a plurality of apertures receivingfasteners therein for fastening the fuel tank to the tunnel.

In some implementations, the lower fuel tank wall includes a lip formedalong a peripheral edge of the lower fuel tank wall. The lip isconnected to the inner surface of the upper fuel tank wall.

In some implementations, the lip of the lower fuel tank wall isconnected to the upper fuel tank wall by at least one of a weldingconnection, a glued connection, and a fastener connection.

In some implementations, the lip of the lower fuel tank wall is weldedto the inner surface of the upper fuel tank wall.

In some implementations, the lip of the lower fuel tank wall includes anangled portion and an elevated portion extending inwardly from theangled portion at an angle relative to the angled portion. The angledportion is generally parallel to a portion of the inner surface of theupper fuel tank wall that is in contact with the angled portion.

In some implementations, the angled portion defines at least part of theperipheral edge of the lower fuel tank wall.

In some implementations, the upper fuel tank wall includes: a left sideportion having a left lower end portion, a right side portion having aright lower end portion, and a central portion being formed integrallywith the left and right side portions. The left side portion extendsgenerally upwardly from the left lower end portion to the centralportion. The right side portion extends generally upwardly from theright lower end portion to the central portion. The central portionextends laterally between the left and right side portions. The lip ofthe lower fuel tank wall is connected to the inner surface of the upperfuel tank wall at the left and right side portions of the upper fueltank wall. The lip of the lower fuel tank wall includes an angledportion and an elevated portion extending inwardly from the angledportion. The angled portion is generally parallel to the inner surfaceof the upper fuel tank wall at the left and right side portions of theupper fuel tank wall.

In some implementations, the lip of the lower fuel tank wall isconnected to the inner surface of the upper fuel tank wall at the leftside portion at a location above a lower edge of the left side portion.The lip of the lower fuel tank wall is connected to the inner surface ofthe upper fuel tank wall at the right side portion at a location above alower edge of the right side portion.

In some implementations, the lip of the lower fuel tank wall isconnected to the inner surface of the upper fuel tank wall at thecentral portion of the upper fuel tank wall.

In some implementations, all corners of a contour of the lower fuel tankwall are rounded.

For purposes of this application, terms related to spatial orientationsuch as forwardly, rearwardly, upwardly, downwardly, left, and right,are as they would normally be understood by a driver of the vehiclesitting thereon in a normal riding position. Terms related to spatialorientation when describing or referring to components or sub-assembliesof the vehicle, separately from the vehicle, should be understood asthey would be understood when these components or sub-assemblies aremounted to the vehicle. Definitions provided herein take precedence overdefinitions of the same term in the document incorporated herein byreference.

Implementations of the present technology each have at least one of theabove-mentioned aspects, but do not necessarily have all of them. Itshould be understood that some aspects of the present technology thathave resulted from attempting to attain the above-mentioned object maynot satisfy this object and/or may satisfy other objects notspecifically recited herein.

Additional and/or alternative features, aspects, and advantages ofimplementations of the present technology will become apparent from thefollowing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present technology, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 is a partially cut-away left side elevation view of a portion ofa snowmobile;

FIG. 2 is a right side elevation view of the frame of the snowmobile ofFIG. 1;

FIG. 3 is a top plan view of the frame of the snowmobile of FIG. 2;

FIG. 4 is a cross-sectional view of the frame of the snowmobile takenalong the line 4-4 of FIG. 3;

FIG. 5 is a right side elevation view of the fuel tank of the snowmobileof FIG. 1 shown in isolation;

FIG. 6 is a perspective view, taken from a rear, top and right side, ofthe fuel tank of FIG. 5;

FIG. 7 is a perspective view, taken from a front, right side, of thefuel tank of FIG. 5;

FIG. 8 is a top plan view of the fuel tank of FIG. 5;

FIG. 9 is a bottom plan view of the fuel tank of FIG. 5;

FIG. 10 is a front elevation view of the fuel tank of FIG. 5;

FIG. 11 is a rear elevation view of the fuel tank of FIG. 5;

FIG. 12 is an exploded perspective view, taken from a front, left side,of the fuel tank of FIG. 5;

FIG. 13 is an exploded perspective view, taken from a rear, left side,of the fuel tank of FIG. 5;

FIG. 14A is a perspective view, taken from a bottom, front and leftside, of a seat base of the seat of the snowmobile of FIG. 1;

FIG. 14B is a right side elevation view of the seat and fuel tank of thesnowmobile of FIG. 1;

FIG. 15 is an enlarged cross-sectional view of a left side portion ofthe frame of the snowmobile of FIG. 1, taken along the line 15-15 ofFIGS. 2 and showing the left side of the fuel tank and the left side ofthe tunnel;

FIG. 16A is a cross-sectional view of a frame of a snowmobile accordingto another implementation, taken along a line corresponding to the line16-16 of FIG. 2; and

FIG. 16B is a close-up of the cross-sectional view of the left sideportion frame of the snowmobile of FIG. 16A, showing the connectionbetween the left side of the fuel tank and the left side of the tunnel.

DETAILED DESCRIPTION

Referring to FIG. 1, a snowmobile 10 includes a forward end 12 and arearward end 14 which are defined consistently with a travel directionof the vehicle 10. The snowmobile 10 includes a vehicle body in the formof a frame or chassis 16 which includes a rear tunnel 18, an enginecradle 20, a front suspension module 22 and an upper support structure24. The tunnel 18 defines a longitudinal centerplane 13 (longitudinallydisposed vertical plane, FIG. 3) of the snowmobile 10. The frame 16 willbe described in further detail below.

An internal combustion engine 50 (shown schematically in FIG. 1) iscarried in an engine compartment defined by the engine cradle 20. A fueltank 52, supported above the tunnel 18, supplies fuel to the engine 50for its operation. The fuel tank 52, which forms part of the upperstructure 24 of the frame 16, will be described below in further detail.Coolant used to cool the engine 50 is circulated through heat exchangers25 (FIG. 2A) mounted to the tunnel 18.

An endless drive track 30 is positioned at the rear end 14 of thesnowmobile 10. The drive track 30 is disposed generally under the tunnel18, and is operatively connected to the engine 50 through a belttransmission system (not shown) and a reduction drive (not shown). Theendless drive track 30 is driven to run about a rear suspension assembly32 connected to the tunnel 18 for propulsion of the snowmobile 10. Theendless drive track 30 has a plurality of lugs 31 extending from anouter surface thereof to provide traction to the track 30.

The rear suspension assembly 32 includes a drive sprocket 34, one ormore idler wheels 36 and a pair of slide rails 38 in sliding contactwith the endless drive track 30. The drive sprocket 34 (shownschematically in FIG. 1) is mounted on a drive axle 35 and defines asprocket axis 34 a. The slide rails 38 are attached to the tunnel 18 byfront and rear suspension arms 40 and one or more shock absorbers 42which include a coil spring (not indicated) surrounding the individualshock absorbers 42. It is contemplated that the snowmobile 10 could beprovided with a different implementation of a rear suspension assembly32 than the one shown herein.

At the rear end of the snowmobile 10, a rear bumper 90, in the form of aU-shaped tubular structure, is connected to the rear end of the tunnel18 and extends rearwardly therefrom.

A straddle-type seat 60 is positioned atop the fuel tank 52. A fillopening 206 (FIG. 3) of the fuel tank 52, covered by a cap 54, isdisposed on the upper surface of the fuel tank 52 in front of the seat60. It is contemplated that the fill opening 206 could be disposedelsewhere on the fuel tank 52. The seat 60 is adapted to accommodate adriver of the snowmobile 10. The seat 60 can also be configured toaccommodate a passenger. A footrest 64, in the form of a footboard, ispositioned on each side of the snowmobile 10 below the seat 60 toaccommodate the driver's feet.

Two skis 70 positioned at the forward end 12 of the snowmobile 10 areeach attached to the front suspension module 22 of the frame 16 througha corresponding front suspension assembly 72. The front suspensionmodule 22 is connected to the front end of the engine cradle 24. Eachfront suspension assembly 72 includes a ski leg 74, supporting arms 76,shock absorbers 78 and ball joints (not shown) for operativelyconnecting to the respective ski leg 74, supporting arms 76 and asteering column 82.

A steering assembly 80, including the steering column 82 and a handlebar84, is provided generally forward of the seat 60. The steering column 82is rotatably connected to the frame 16. The lower end of the steeringcolumn 82 is connected to the ski legs 74 via steering rods 83 (the leftend of the left steering rod 83 can be seen in FIG. 1). The handlebar 84is attached to the upper end of the steering column 82. The handlebar 84is positioned in front of the seat 60. The handlebar 84 is used torotate the steering column 82, and thereby the skis 70, in order tosteer the vehicle 10. A throttle operator (not shown) in the form of athumb-actuated throttle lever is mounted to the right side of thehandlebar 84. Other types of throttle operators, such as afinger-actuated throttle lever are also contemplated. A brake actuator(not indicated), in the form of a hand brake lever, is provided on theleft side of the handlebar 84 for braking the snowmobile 10 in a knownmanner.

At the front end 12 of the snowmobile 10, fairings 94 enclose the engine50 and the belt transmission system, thereby providing an external shellthat not only protects the engine 50 and the transmission system, butcan also be decorated to make the snowmobile 10 more aestheticallypleasing. The fairings 94 include a hood 96 and one or more side panelswhich can be opened to allow access to the engine 50 and the belttransmission system when this is required, for example, for inspectionor maintenance of the engine 50 and/or the transmission system. Awindshield 98 connected to the fairings 94 acts as a wind screen tolessen the force of the air on the rider while the snowmobile 10 ismoving. The windshield 98 may be connected directly to the handlebar 84.

The snowmobile 10 includes other components such as a display cluster,an exhaust system, an air intake system, and the like. As it is believedthat these components would be readily recognized by one of ordinaryskill in the art, further explanation and description of thesecomponents will not be provided herein.

The frame 16 will now be described in more detail with reference toFIGS. 2 to 4. As previously mentioned, the frame 16 of the snowmobile 10includes the tunnel 18, the engine cradle 20, the front suspensionmodule 22, and the upper structure 24 which includes the fuel tank 52.

The tunnel 18 generally forms an inverted U-shaped structure when viewedfrom the front or back. With reference to FIGS. 2 to 4, the tunnel 18includes a top surface 120 extending generally horizontally, a left sidesurface 122 extending generally vertically and a right side surface 122extending generally vertically. A left bevel surface 124 connects theleft edge of the top surface 120 to the upper edge of the left sidesurface 122. A right bevel surface 124 connects the right edge of thetop surface 120 to the upper edge of the right side surface 122. Eachbevel surface 124 is planar and extends downwardly and laterallyoutwardly from the horizontal top surface 120 to the correspondingvertical side surface 122. Each bevel surface 124 forms an obtuse anglewith the horizontal top surface 120. Each bevel surface 124 also formsan obtuse angle with the corresponding vertical side surface 122. Eachbevel surface 124 allows for connection of a corresponding side portion224 of the fuel tank 52 as will be described further below. A portion125 of the tunnel 18 connected to the corresponding side tunnel surface122 just below the bevel surface 124 helps to reduce noise andvibrations caused by the tunnel 18. It is contemplated that the portion125 could also be used to support the fuel tank 52.

As best seen in FIG. 2, when viewed from a lateral side, the top surface120 slopes gently upwardly from the front to the rear of the tunnel 18when the snowmobile 10, without any load (cargo or riders), is at reston a horizontal surface. It is contemplated that the entire length ofthe top surface 120 could be horizontal, or that there could be morethan one slope along the length of the tunnel 18. It is alsocontemplated that a portion of the top surface 120 could be curved in alateral or longitudinal direction. With reference to FIG. 3, the topsurface 120 has a rectangular gap 121 extending longitudinally along thecenterplane 13. The gap 121 extends from the rear end of the tunnel 18towards the front end of the tunnel 18. It is contemplated that the gap121 could be shaped and sized differently than as shown. The heatexchanger 25 is disposed in the gap 121 of the top surface 120. Thecoolant flowing through the heat exchanger 25 is cooled by cool airflowing along the surfaces of the heat exchanger 25 disposed in the gap121 and the snow being thrown upwards onto the lower surface of the heatexchanger 25 by the turning track 40 disposed below the tunnel 18.

With reference to FIGS. 2 to 4, a central arm 90 a of the bumper 90 isdisposed rearward of the rear end tunnel 18 and generally aligned withthe top tunnel surface 120. A left end of the central arm 90 a isconnected to a downwardly and forwardly extending left arm 90 b and itsright end connected to a downwardly and forwardly extending right arm 90b. The left arm 90 b extends downwardly and forwardly to the bottom edgeof the left tunnel surface 122 and then along the bottom edge of theleft tunnel surface 122. The front end of the left arm 90 b is disposedforward of the rear end of the left footrest 64. The right arm 90 bsimilarly extends downwardly and forwardly to the bottom edge of theright tunnel surface 122 and therealong. The front end of the right arm90 b is disposed forward of the rear end of the right footrest 64. It iscontemplated that the bumper 90 could be shaped differently than asshown herein.

With reference to FIGS. 2 and 4, each of the left and right sidesurfaces 122 of the tunnel 18 has an opening 126 which receives thefront drive axle (not shown). The front portion of the left side surface122 around the opening 126 is reinforced for additional rigidity, as canbe seen when viewed from a lateral side. The left footrest 64 extendsleftwardly from the bottom edge of the left side surface 122, and theright footrest 64 extends rightwardly from the bottom edge of the rightside surface 122. Each footrest 64 is formed integrally with thecorresponding one of the tunnel side surfaces 122. A toehold 66 extendsupward from the front edge of each footrest 64. Each of the left andright toeholds 66 has a generally vertical front portion 66 a thatextends upwardly from the front edge of the footrest 64, a generallyhorizontal middle portion 66 b that extends rearwardly from the top ofthe front portion 66 a and a rear portion 66 c that extends upwardlyfrom the rear end of the middle portion 66 b. A footrest support 62connects the front end of each footrest 64 to a rear portion 130 of theengine cradle 20.

With reference to FIGS. 2 to 4, the engine cradle 20 is attached to thefront end of the tunnel 18 and extends forwardly therefrom. In theillustrated implementation of the engine cradle 20, the rear portion 130of the engine cradle 20 extends generally vertically and is connected tothe front of the tunnel 18. A generally horizontal bottom portion 132 ofthe engine cradle 20 extends forwardly from the bottom of the rearportion 130, and a generally vertical front portion 134 rises upwardsfrom the bottom portion 132 of the engine cradle 20. The engine 50 issupported by the engine cradle 20 in a manner which would be determinedby the size and shape of the engine 50. Engine cradles having differentshapes and including components different than as described above arealso contemplated. The engine 50 can be supported on the bottom portion132 of the engine cradle 20 or can also be solely and/or simultaneouslysupported by other areas of the engine cradle 20, tunnel 18 and/or frontsuspension module 22. On the right side of the engine cradle 20, as bestseen in FIGS. 2 and 3, a generally horizontal upper bar 136 extendsbetween the upper ends of the front and rear portions 134, 130 of theengine cradle 20. The right upper bar 136 is spaced from the generallyhorizontal bottom portion 132 in order to provide additional structuralrigidity to the engine cradle 20. In the illustrated implementation, aleft upper bar 138 is also provided on the left side of the enginecradle 20, connecting between the upper ends of the front and rearportions 134, 130 of the engine cradle 20 and being spaced from thebottom portion 132. In the illustrated implementation, the bars 136, 138are removably mounted to the front and rear portions 134, 130. It iscontemplated that one or both of the upper bars 136, 138, could beomitted, or configured differently than as shown.

With reference to FIGS. 2 to 4, the front suspension module 22, whichattaches the front suspension assembly 16 to the snowmobile 10, isattached to the front portion 134 of the engine cradle 20. The frontsuspension module 22 extends forwardly from the engine cradle 20. Thefront suspension module 22 includes left and right front suspensionmounting brackets 140. Each bracket 140 forms an inverted generallyV-shaped structure extending forwardly from the front portion 134 of theengine cradle 20. Each front suspension mounting bracket 140 has thecorresponding front suspension assembly 72 attached thereto. Other typesof suspension mounting brackets are also contemplated to accommodatedifferent types of front suspension assemblies 72. The front suspensionmodule 22 and the engine cradle 20 also support a portion of an exhaustsystem (not shown) connected to the engine 50.

With reference to FIGS. 2 to 4, the upper support structure 24 includesan upper forward support 102, an upper column 103, and the fuel tank 52.The upper forward support 102 includes left and right forward supportbraces 108. The lower end of each of the left and right forward supportbraces 108 is attached to the corresponding one of the left and rightfront suspension mounting bracket 140 at the upper end thereof (apex ofthe inverted V-shaped bracket 140). A laterally extending frame member107 connects between the lower ends of the two forward support braces108. The frame member 107 is also connected to the top of the frontsuspension mounting brackets 140. The apex of the left mounting bracket140, the left end of the frame member 107 and the bottom end of the leftforward support brace 108 are connected together at a common connectionpoint 141 on the left side. Similarly, the apex of the right mountingbracket 140, the right end of the frame member 107 and the bottom end ofthe right forward support brace 108 are connected together at a commonconnection point 141 on the right side. Each forward support brace 108extends upwards, rearwards and laterally inwards to an upper end. Asteering bracket 148 positioned above the engine cradle 20 is connectedto the upper ends of the forward support braces 108. The steeringbracket 148 is formed of a pair of laterally spaced plates 148 a and twolateral connectors 148 b extending therebetween. Each of the plates 148a extends vertically and longitudinally and has a triangular shape whenviewed from a lateral side. The bottom end of each steering bracketplate 148 a is connected to the upper end of the corresponding forwardsupport brace 108. The steering column 82 is rotatably inserted throughthe steering bracket 148 between the braces 108. The steering column 82extends downwards and forwards from the handlebar 84 through thesteering bracket 148 to the front suspension assembly 72 (connection notshown in figures) for rotating the skis 70 and steering the snowmobile10. It is contemplated that the steering bracket 148 could extendfurther outwards in the lateral direction than as shown in the figures.The forward support braces 108 are formed as extruded hollow tubes madeof metal or other suitably strong materials, however, the disclosure isnot intended to be limited to this particular material, assembly methodor configuration. For example, it is contemplated that the forwardsupport braces 108 could have a different cross-section or be made bymolding or casting. It is also contemplated that the forward supportbraces 108 may be constructed according to a monocoque orpseudo-monocoque technique instead of having a tubular construction asin the illustrated implementation.

With reference to FIGS. 2 to 4, an upper column 103 extends upwards fromthe engine cradle 20 to support the steering bracket 148. The uppercolumn 103 includes a left leg 118 which extends upwardly, forwardly andlaterally inwardly from the engine cradle portion 130. The left steeringbracket plate 148 a is connected to the upper end of the left leg 118rearward of the connection of the steering bracket plate 148 a to theleft forward support brace 108. It is contemplated that the upper column103 could include a right upper column leg connecting the right steeringbracket plate 148 a to the engine cradle 20. It is also contemplatedthat the upper column leg 118 could be connected to the left forwardsupport brace 108 instead of the steering bracket 148. In theillustrated implementation, the left upper column leg 118 is in the formof a straight, tubular rod, but it is contemplated that the legs 118could also have a bend or a curve. For example, the leg 118 could extendupwardly from the engine cradle 20 and then bend laterally inwardly tothe steering bracket 148. It is also contemplated that the leg 118 couldnot be tubular. For example, the leg 118 could be in the form of a solidrod. It is further contemplated that the upper column 103 could beconstructed as a single inverted U-shaped structure having two legs 118.

The fuel tank 52 is mounted on the top surface 120 of the tunnel 18 andis rigidly secured thereto as will be discussed below. The fuel tank 52extends upwards and forwards from the tunnel 18 to connect to thesteering bracket 148 and thereby to the forward support braces 108. Thefuel tank 52 is also rigidly secured the steering bracket 148. Thisconfiguration of the frame 16 in which the fuel tank 52 connects thetunnel 18 to the upper forward support 102 enhances the torsional andstructural rigidity of the frame 16 by enabling transfer of torques andforces from the upper forward support 102 to the tunnel 18 via the fueltank 52. The fuel tank 52 is secured removably to the steering bracket148 and tunnel 18 in order to allow removal of the fuel tank 52 formaintenance, repairs, and/or replacement.

With reference to FIGS. 1 to 3, a pyramidal structure is formed by thecooperating components of the frame 16, namely the fuel tank 52, theforward supports braces 108, the tunnel 18, engine cradle 20 and thefront suspension module 22. The contact area between the fuel tank 52and the tunnel 18 is larger than the contact area between the fuel tank52 and the forward support braces 108. The fuel tank 52 tapers in widthas it rise upwards from the tunnel 18 toward the steering bracket 148and the forward support braces 108. This pyramidal structure increasesthe torsional rigidity of the frame 16 about axes perpendicular to thefront drive axle axis 34 a, compared to some snowmobile frames without apyramidal structure. With reference to FIG. 2, when viewed from alateral side, the cooperation between the forward supports braces 108,the fuel tank 52, the tunnel 18, engine cradle 20 and the frontsuspension module 22 forms a generally triangular structure whichincreases the resistance to bending along axes parallel to the frontdrive axle axis 34 a.

The fuel tank 52 will now be described in further detail with referenceto FIGS. 2 to 15.

With reference to FIGS. 2 and 4, the fuel tank 52 has a rear portion 202extending along the top surface 120 of the tunnel 18, and a neck portion204 extending upwardly and forwardly from the lower portion 202 to anupper end portion 230 connected to the steering bracket 148. As can beseen in FIG. 3 the fuel tank 52 has a generally oblong shape when viewedfrom the top. When viewed from the front (FIG. 10) or rear (FIG. 11),the fuel tank 52 has a generally triangular shape.

With reference to FIGS. 12, 13 and 15, the fuel tank 52 is formed by anupper wall 220 and a lower wall 240 as will be described below. The fueltank 52 is connected to the tunnel 18 and the steering bracket 148 viathe upper wall 220. With reference to FIGS. 2 to 4, the upper endportion 230 of the fuel tank 52 extends longitudinally forward of theupper column leg 118 and is connected to the steering bracket 148. Aleft lower end portion 226 of the fuel tank 52 is connected to the leftbevel surface 124 of the tunnel 18 and a right lower end portion 226 isconnected to the right bevel surface 124 of the tunnel 18.

With reference to FIGS. 5 to 12, the upper wall 220 of the fuel tank 52has an upper wall central portion 222, an upper wall left side portion224, and an upper wall right side portion 224. The upper wall centralportion 222 extends laterally from the upper wall left side portion 224to the upper wall right side portion 224. The upper wall left sideportion 224 extends generally downwardly and leftwardly from the leftside of the upper wall central portion 222. The upper wall right sideportion 224 extends generally downwardly and rightwardly from the rightside of the upper wall central portion 222. The left side portion 224includes the left lower end portion 226 and the right side portion 224includes the right lower end portion 226. The upper end portion 230 ofthe upper wall 220 is formed by the central portion 222, as well as theleft and right side portions 224.

With reference to FIGS. 5 to 12, the upper wall central portion 222extends generally horizontally in the rear portion 202 of the fuel tank52 except at the rear end where it extends generally verticallydownwardly to a rear edge 228. The rear edge 228 of the upper wall 220is disposed above the heat exchanger 25 and is generally aligned withthe rear end of the footrest 64 in the longitudinal direction. The upperwall central portion 222 extends forwardly and upwardly to form the neckportion 204 and the upper end portion 230. The width of the upper wallcentral portion 222 in the neck portion 204 tapers towards the upper endportion 230 as can be seen in FIG. 6.

With reference to FIGS. 2 to 6, the fill opening 206 is defined in theupper wall central portion 222 forming the neck portion of the fuel tank52. A cylindrical fill tube 207 is connected to the fill opening 206 andextends upwardly and rearwardly from the rearwardly and upwardly facingsurface of the central portion 222. The open end of the fill tube 207 isselectively sealed by a removable cap 54 (FIG. 1). In the illustratedimplementation, the open end of the fill tube 207 and the cap 54 arethreaded, and the open end of the fill tube 207 is sealed by screwingthe cap 54 thereon. It is contemplated that the fill tube 207 and thecap 54 could be configured differently. For example, the cap 54 could belatched, or otherwise locked, to the open end of the fill tube 207 forsealing the fill tube 207. The fill tube 207 is disposed longitudinallyforward of the seat 60. The fill tube 207 is disposed above the drivesprocket 34 so as to have a longitudinal position between the front andrear edges of the drive sprocket 34 as can be seen in FIG. 1. The filltube 207 is longitudinally forward of the rotational axis 34 a of thedrive axle. The fill tube 207 is rearward of the footrest support 62. Itis contemplated that the fill opening 206 could be formed elsewhere onthe neck portion 204 of the fuel tank 52.

With reference to FIGS. 10 and 11, the upper wall left side portion 224extends forwardly, rightwardly and upwardly from the left lower endportion 226 to the left side of the upper end portion 230. Similarly,the upper wall right side portion 224 extends forwardly, leftwardly andupwardly from the right lower end portion 226 to the right side of theupper end portion 230. When viewed from the front or the rear, each ofthe upper wall side portions 224 extends at generally the same anglewith respect to the vertical in the fuel tank rear portion 202 as in thefuel tank neck portion 204.

With reference to FIGS. 3, 4 and 8, in the upper end portion 230, eachof the upper wall side portions 224 extends generally longitudinallyparallel to the longitudinal centerplane 13. Thus, each of the upperwall side portions 224 has a bend near the upper end portion 230. Theupper wall 220 is reinforced by a bracket 280 near the upper end portion230. It is contemplated that the bracket 280 could be in the form of aleft reinforcing bracket extending from the upper end 230 along the leftside portion 224 to the left bevel surface 124 of the tunnel 18 and aright reinforcing bracket extending from the upper end 230 along theright side portion 224 to the right bevel surface 124 of the tunnel 18.The fuel tank 52 is connected to the steering bracket 148 by the upperend portion 230. Each of the left and right side portions 224 has a pairof apertures 231 extending therethrough in the reinforced upper endportion 230. As can be seen in FIG. 4, the rear end of the left sideplate 148 a of the steering bracket 148 is placed on the inner surfaceof the left side portion 224 facing laterally inwardly towards the rightside portion 224. The left plate 148 a of the steering bracket 148 isconnected to the fuel tank 52 by bolts inserted through the apertures231 into the left side plate 148 a of the steering bracket 148. The rearend of the right side plate 148 a of the steering bracket 148 issimilarly placed on the inner surface of the upper wall right sideportion 224 facing laterally inwardly towards the upper wall left sideportion 224 and connected thereto by bolts inserted through theapertures 231. It is contemplated that the steering bracket plates 148 acould be disposed on the outer surfaces of the upper wall side portions224 (surfaces facing away from the central portion 222). It is alsocontemplated that the steering bracket 148 could be configureddifferently than as shown herein and/or connected to the upper endportion 230 of the fuel tank 52 differently than as shown herein.

The right side portion 224 of the upper wall 220 will now be describedwith reference to FIGS. 2 to 12. The left side portion 224, is a mirrorimage of the right side portion 224, and as such, corresponding featuresof the left and right side portions 224 have been labeled with the samereference numbers and will not be described herein again in detail.

With reference to FIGS. 5 to 12, the right lower end portion 226 hasfive apertures 236 which are aligned with corresponding apertures (notshown) of the right bevel surface 124 and fastened thereto by bolts (notshown). The angle, with respect to the vertical, of the right bevelsurface 124 of the tunnel 18 corresponds to the inclination angle of theplanar right lower end portion 226, with respect to the vertical. Theupper wall right side portion 224 can thus be directly fastened to thebevel surface 124 without using any additional brackets. The upper wallright side portion 224 extends upwardly and laterally inwardly from theright lower end portion 226 to the upper wall central portion 222. Theupper wall right side portion 224 extends continuously upwardly from theright lower end portion 226.

With reference to FIG. 5, the right side portion 224 is generally planarin the rear portion 202 of the fuel tank 52 except for bends 232 and 238extending generally vertically. The right side portion 224 has severalbends 232, each formed along a corresponding bend axis 232 a extendingin a generally upwardly and forwardly direction. Each bend axis 232 apasses through the upper end portion 230 and along the right side of theneck portion 204 to the lower end portion 226. Some of the bends 232extend downward from the upper end portion 230, while other bends extendupward from the lower end portion 226. The bends 232 serve to increasethe inertial strength of the upper wall 220 and help to preventbuckling. The bends 232 define a brace portion 234 in the upper wallright side portion 224 which functions as an upper rear support brace ofthe snowmobile frame 16 for transmitting forces from the forward supportbraces 108 to the tunnel 18. The brace portion 234 includes the part ofthe right side portion 224 encompassed between a forwardmost bend axis232 a and a rearwardmost bend axis 232 a as can be seen in FIG. 5. Arear bend 238 is formed in the right side portion rearward of the rightlower end portion 226. Two of the apertures 236 are defined in the braceportions 234, one aperture 236 is disposed rearward of the brace portion234 and two apertures 236 are disposed forward of the brace portion 234.The rear bend 238 is disposed near the rear end of the fuel tank 52.Rearward of the rear bend 238, the right side portion 224 extendslaterally inwardly towards the rear end, as can be seen in FIG. 7. Thebrace portion 234 described above, having the generally vertical bends232, 238 provides greater strength and resistance to forces ofcompression and torsion than an unbent sheet metal structure. Withreference to FIGS. 5 to 12, outside of the brace portion 234 and forwardof the bend 238, the right side portion 224 is generally planar.

With reference to FIG. 14B, and as mentioned above, the seat 60 issupported on the fuel tank 52. As can be seen in FIG. 14A and 14B, theseat 60 includes a seat base 61 and a seat cushion 60 a that is attachedto the upper surface of the seat base 61. The seat base 61 iscomplementary to the upper surface of the fuel tank upper wall 220 andfits congruously thereon. The central portion 222 of the fuel tank upperwall 220 forms a number of laterally extending recesses 264 that arecomplementary to protrusions formed in the downward facing surface ofthe seat base 61. The fuel tank 52 is designed to be used with aremovable seat 60. The central portion 222 of the upper wall 220 isprovided with six seat fastening members 260 and a seventh larger andresilient seat fastening member 262 for fastening the seat 60 to thefuel tank 52. In the illustrated implementation of the fuel tank 52, theseat fastening members 260, 262 are in the form of hooks but it iscontemplated that the seat fastening members 260 could be other than asshown, and that there could be more or less than seven seat fasteningmembers 260, 262. A front hook 260 and a rear hook 260 are disposedalong the longitudinal centerline 13. The front hook 260 is disposedjust below the neck portion 204, while the rear hook 260 is disposednear the rear end of the longitudinal centerline 13. Two hooks 260 aredisposed on either side of the longitudinal centerline 13 just rearwardof the front hook 260. Two hooks 260 are disposed on either side of thelongitudinal centerline 13 just forward of the rear hook 260. Each ofthe hooks 260 projects upwards from the surface of the upper fuel tankwall 220 and then rearward. The hook 262 disposed in the lower end ofthe neck portion 204 forward of the front hook 260 and disposed alongthe longitudinal centerline 13. The hook 262 projects upwardly from theupper surface of the upper fuel tank wall 220 and then forwardly. Thefront end of the hook 262 forms a groove 262 a facing forwardly. Theseat base 61 includes six slots 260′ which receive the hooks 260 forfastening the seat base 61 to the fuel tank 252. The seat base 61 alsohas a tongue-like structure 262′ extending forwardly and upwardly fromthe front end of its bottom surface. The seat base 61 is positioned onthe upper fuel tank wall 220 so as to align the hooks 260 with thecorresponding seat base slots 260′, and then pushed forward so that thehooks 260 are received in the corresponding seat base slots 260′. Oncethe hooks 260 are received in the slots 260′, the seat base 61 is pushedfurther forward so that the rear end 262 a′ of the tongue 262′ slipsinto the forward facing groove 262 a of the hook 262. When the tongue262′ is engaged with the hook 262, the seat base 61 is prevented frommoving rearwards. The configuration of the hooks 260, 262 thus preventsrelative movement between the fuel tank 52 and the seat 60 in thevertical, lateral and longitudinal directions. The front end of thetongue 262′ remains visible in the front end of the seat 60 when theseat base 61 is fastened to the fuel tank 52 as the front end of theseat base 61 is spaced form the upper surface of the fuel tank upperwall 220. The tongue 262′ is used for unfastening the seat base 61 fromthe fuel tank 52. The tongue 262′ can be pulled upwards to disengage therear end 262 a′ of the tongue 262 from the groove 262 a of the hook 262.The seat base 61 can then be pushed rearwards until the fuel tank hooks260 slide out of the corresponding seat base slots 260′. Once the fueltank hooks 260 are free of the seat base slots 260′, the seat base 61can be removed from the fuel tank upper wall 220. U.S. Pat. No.7,980,629 B2, issued Jul. 19, 2011, the entirety of which isincorporated herein by reference, provides additional details aboutremovable seats, and means for attachment to the fuel tank 52.

With reference to FIGS. 4, 7, 9, 10, 12, 13 and 15 the lower wall 240 isconnected to the inner surface of the upper wall 220 so as to enclose avolume 250 (FIG. 4) therebetween. The lower wall 240 extends laterallyfrom the left side portion 224 of the upper wall 220 to the right sideportion 224 thereof. The lower wall 240 extends generally horizontallyin the rear portion 202 of the fuel tank 52. In the neck portion 204 ofthe fuel tank 52, the lower wall 240 extends upwardly and forwardly toan upper end portion 244 which extends generally vertically. In the neckportion 204 of the fuel tank 252, the lower wall 240 is disposed infront of the upwardly and forwardly extending central portion 222 of theupper wall 220. The upper wall upper end portion 230 extends above thelower upper end portion 244 and longitudinally forwardly thereof.

The lower wall 240 has a lip 242 formed along its edge, and is connectedto the upper wall 220 by the lip 242. The lip 242 at the rear edge ofthe lower wall 240 is connected to the inner surface of the upper wall220 just above the rear edge 228. The lip 242 extending along the leftedge of the lower wall 240 is connected to the inner surface of the leftside portion 224 of the upper wall 220 at a location above its loweredge. The lip 242 extending along the right edge of the lower wall 240is connected to the inner surface of the right side portion 224 at alocation above its lower edge. The left and right lower end portions 226of the upper fuel tank wall 220 extend lower than lip 242. A vibrationdamper 252 (best seen in FIG. 16A) is placed between the lower wall 240and the heat exchanger disposed across the top of the gap 121 of thetunnel 18 to reduce transmission of vibrations from the tunnel 18 viathe heat exchanger 25 to the lower fuel tank wall 240. The lower wall240 is disposed spaced from the tunnel 18 as can be seen clearly in FIG.15.

In the neck portion 204 of the fuel tank 52, the lip 242 of the upperend portion 244 is connected to the central portion 222 of the upperwall 220 just below the upper end portion 230. The steering bracket 148is thus connected to the left and right side portions 224 of the upperwall 220 longitudinally forward of the connection of the lip 242. Thelower wall 240 is thus spaced from the steering bracket 148.

The position of the connection of the lower wall 240 to the upper wall220 ensures that forces transmitted from the forward support 102 to thetunnel 18 via the fuel tank 52 are transmitted through the upper wall220 without passing through the lower wall 240. Thus, the connectionbetween the upper and lower fuel tank walls 220, 240 is not compromisedby the forces being transmitted via the fuel tank 52 between the frontand rear of the snowmobile frame 16.

In the illustrated implementation of the fuel tank 52, the lip 242 isconnected to the upper fuel tank wall 220 by welding. It is howevercontemplated that the lower wall 240 could be connected to the upperwall 220 by means other than welding. For example, the lower wall 240could be connected to the upper wall 220 by a fasteners, by gluing, orby Friction Stir Welding.

With reference to FIGS. 4, 7, 9 and 10, in the neck portion 204 of thefuel tank 52, the lower wall 240 bulges forwardly away from the upperwall 220 to form a rearward facing recess 254. The recess 254 isdisposed just below the upper end portion 244. As can be seen best inFIG. 4, the rearward facing recess 254 is disposed directly opposite thefuel tank fill opening 206 defined in the upper wall 220 such that afuel nozzle inserted into the fuel tank 52 through the fill opening 206and fill tube 207 is received in the recess 254. The shape and size ofthe recess 254, in combination with the length of the fill tube 207, isselected so as to accommodate a typical fuel nozzle. The recess 254allows the fill opening 206 to be located in the neck portion 204 whileallowing a spacing between the upper and lower fuel tank walls 220, 240outside of the recess 254 to be relatively smaller than the length ofthe fuel nozzle.

The lower wall 240 has a fuel outlet opening 208 defined in the frontfacing surface of the front portion of the lower wall 240 below therecess 254. The fuel outlet opening 208 is defined in a portion wherethe lower fuel tank wall 240 extends rearwardly to form a circularrecess 209. As can be seen best in FIG. 4, a fuel pump 210 is housedinside the volume 250 of the fuel tank 52 and is connected to fueloutlet opening 208. The fuel pump 210 is used to feed fuel from the fueltank 10 to the fuel injection system (not shown) of the engine 50. Thefuel outlet opening 208 is disposed rearward of the fill opening 206 andvertically lower thereof.

Below the fuel outlet opening 208, a central portion of the lower fueltank wall 240 bulges rearwardly to form another forward facing recess256. The recess 256 is formed to accommodate other components of thesnowmobile.

Each of the upper and lower fuel tank walls 220, 240 is formed of asingle piece of sheet metal. The sheet metal piece is stamped orsubjected to super plastic forming to form the structure as describedabove. A lower portion of the fill tube 207 is formed with the upperwall 220 and the threaded upper portion of the fill tube 207 is formedseparately and welded to the upper portion thereafter. It is howevercontemplated that the entire fill tube 207 could be formed with theupper wall 220. FIG. 16A shown another implementation of a snowmobile10′ in which the fuel tank 52 is shown before the fill tube 207 iswelded to the inlet 206. In the illustrated implementation, the upperand lower fuel tank walls 220, 240 are formed of aluminum, but it iscontemplated that the fuel tank 52 could be constructed of othersuitable materials and/or by other suitable processes than thosedescribed herein.

Forming the entire upper wall out of a single piece of sheet metalallows the upper end portion 230 and the lower end portions 226 to beconnected to other vehicle portions (steering bracket 148 and tunnel 18respectively) directly without the need for using separate attachmentbrackets. Connecting the fuel tank 52, directly to the other snowmobileportions without using additional brackets helps to reduce the overallweight of the snowmobile 10, and also to reduce assembly complexity andcost.

The fuel tank 10 described herein is a structural fuel tank 10,providing a very stable and rigid support structure for the snowmobile1, with enhanced torsional and structural rigidity. The structural fueltank 10 helps prevent bending or torsion between the tunnel 18 and theengine cradle 102 and/or the front suspension module 104. The frame 16,as described herein, thus helps reduce torsional bending in thesnowmobile 10, and helps prevent transmission of bending moments fromthe front 2 to rear 3 of the snowmobile 10. Incorporating the fuel tank10 into the frame 16 allows for elimination of rear support braces forconnecting the forward support braces 108 to the tunnel 18 withoutsubtracting from the rigidity or the stability of the frame 16 and ofthe snowmobile 10. A reduction of components without loss offunctionality enables a cheaper and more efficient manufacturingprocess. Elimination of the rear support braces and incorporation of thefuel tank into the frame 16 simplifies assembly and disassembly of thesnowmobile and also provides more flexibility in the configuration ofits components and their placement in the snowmobile relative to eachother. Additionally, the snowmobile 10 is made lighter in weight andstronger in structure by using the frame 16 having the fuel tank 10 asdescribed herein as compared to frames in which the tunnel 18 isconnected to the steering bracket 148 by rear support braces that aredistinct from the fuel tank.

With reference to FIGS. 16A and 16B, another implementation of thesnowmobile 10′ is shown. The snowmobile 10′ is similar to the snowmobile10 described above. Corresponding and similar features of the snowmobile10 and 10′ have been labelled with the same reference numbers, and willnot be discussed herein again.

The lower left end portion 226 of the fuel tank 52 of the snowmobile 10′has a recessed portion 236′ around each aperture 236 through which abolt is inserted to fasten the fuel tank 52 to the tunnel bevel surface124. The inner surface (surface facing the tunnel 18) of the recessedportions 236′ is in contact with the left bevel surface 124 as seen bestin FIG. 16B. The inner surface of the left lower end portion 226 abovethe recessed portion 236′ is spaced from the tunnel bevel surface 124.Each recessed portion 236 receive the head of a bolt (not shown) bywhich the fuel tank 52 is fastened to the tunnel 18. The recessedportion 236′ helps to keep the head of the bolt from projectinglaterally outwardly of the surface of the left lower end portion 226,and helps to reduce the possibility something being inadvertently beinghooking to the bolt. It is contemplated that the recessed portions 236′could be omitted as in the snowmobile 10 of FIGS. 1 to 4. The lowerright end portion 226 of the fuel tank 52 of the snowmobile 10′ is amirror image of the lower left end portion thereof, and as such will notbe described herein again.

Modifications and improvements to the above-described implementations ofthe present may become apparent to those skilled in the art. Theforegoing description is intended to be exemplary rather than limiting.The scope of the present is therefore intended to be limited solely bythe scope of the appended claims.

What is claimed is:
 1. A fuel tank for a snowmobile comprising: a lowerfuel tank wall; and an upper fuel tank wall, the lower fuel tank wallbeing connected to an inner surface of the upper fuel tank wall, each ofthe lower and upper fuel tank walls being constructed of a single pieceof sheet metal, the lower and upper fuel tank walls enclosing a volumetherebetween configured to be in fluid communication with an engine ofthe snowmobile, the fuel tank being configured to be removably connectedto a tunnel and a forward support of the snowmobile by the upper fueltank wall, the upper fuel tank wall comprising: a left lower end portionfor connecting the fuel tank to the tunnel on a left side of alongitudinal centerplane of the snowmobile; a right lower end portionfor connecting the fuel tank to the tunnel on a right side of thelongitudinal centerplane of the snowmobile; and an upper end portion forconnecting the fuel tank to the forward support.
 2. The fuel tank ofclaim 1, wherein the upper fuel tank wall comprises: a left side portionextending generally vertically and comprising the left lower endportion; a right side portion extending generally vertically andcomprising the right lower end portion; and a central portion beingformed integrally with the left and right side portions, the left sideportion extending generally upwardly from the left lower end portion tothe central portion, the right side portion extending generally upwardlyfrom the right lower end portion to the central portion, and the centralportion extending laterally between the left and right side portions. 3.The fuel tank of claim 2, wherein the lower fuel tank wall extendsgenerally horizontally from the left side portion to the right sideportion of the upper fuel tank wall.
 4. The fuel tank of claim 1,wherein the upper fuel tank wall defines a fill opening in fluidcommunication with the volume.
 5. The fuel tank of claim 1, furthercomprising: at least one seat fastening member for fastening a seat ofthe snowmobile to the fuel tank, the at least one seat fastening memberbeing connected to an outer surface of the upper fuel tank wall facingaway from the lower fuel tank wall.
 6. The fuel tank of claim 1,wherein, each of the upper and lower fuel tank walls is formed by oneof: stamping; and super plastic forming.
 7. The fuel tank of claim 1,wherein each of the left and right lower end portions of the upper fueltank wall defines a plurality of apertures receiving fasteners thereinfor fastening the fuel tank to the tunnel.
 8. The fuel tank of claim 1,wherein the lower fuel tank wall comprises a lip formed along aperipheral edge of the lower fuel tank wall, the lip being connected tothe inner surface of the upper fuel tank wall.
 9. The fuel tank of claim8, wherein the lip of the lower fuel tank wall is connected to the upperfuel tank wall by at least one of: a welding connection; a gluedconnection; and a fastener connection.
 10. The fuel tank of claim 9,wherein the lip of the lower fuel tank wall is welded to the innersurface of the upper fuel tank wall.
 11. The fuel tank of claim 8,wherein the lip of the lower fuel tank wall comprises: a first portion;and a second portion extending inwardly from the first portion at anangle relative to the first portion, the first portion being generallyparallel to a portion of the inner surface of the upper fuel tank wallthat is in contact with the first portion.
 12. The fuel tank of claim11, wherein the first portion defines at least part of the peripheraledge of the lower fuel tank wall.
 13. The fuel tank of claim 8, wherein:the upper fuel tank wall comprises: a left side portion comprising theleft lower end portion; a right side portion comprising the right lowerend portion; and a central portion being formed integrally with the leftand right side portions, the left side portion extending generallyupwardly from the left lower end portion to the central portion, theright side portion extending generally upwardly from the right lower endportion to the central portion, and the central portion extendinglaterally between the left and right side portions; the lip of the lowerfuel tank wall is connected to the inner surface of the upper fuel tankwall at the left and right side portions of the upper fuel tank wall;and the lip of the lower fuel tank wall comprises: a first portion; anda second portion extending inwardly from the first portion, the firstportion being generally parallel to the inner surface of the upper fueltank wall at the left and right side portions of the upper fuel tankwall.
 14. The fuel tank of claim 13, wherein: the lip of the lower fueltank wall is connected to the inner surface of the upper fuel tank wallat the left side portion at a location above a lower edge of the leftside portion; and the lip of the lower fuel tank wall is connected tothe inner surface of the upper fuel tank wall at the right side portionat a location above a lower edge of the right side portion.
 15. The fueltank of claim 13, wherein the lip of the lower fuel tank wall isconnected to the inner surface of the upper fuel tank wall at thecentral portion of the upper fuel tank wall.
 16. The fuel tank of claim1, wherein all corners of a contour of the lower fuel tank wall arerounded.
 17. The fuel tank of claim 1, wherein: the left lower endportion of the upper fuel tank wall extends vertically lower than aconnection between a left side of the lower fuel tank wall and the upperfuel tank wall; and the right lower end portion of the upper fuel tankwalls extends vertically lower than a connection between a right side ofthe lower fuel tank wall and the upper fuel tank wall.
 18. The fuel tankof claim 1, wherein along a span of a connection between the lower andupper fuel tank walls, part of the upper fuel tank wall extendsvertically lower than the connection between the lower and upper fueltank walls.